Liquid detergent and cleaning compositions in the form of microemulsions, both oil-in-water and water-in-oil, have been disclosed in the prior art.
EP 137 616A (Procter & Gamble) discloses liquid detergent compositions prepared from conventional detersive surfactants and other conventional detergent ingredients, plus a grease-cutting solvent. The compositions contain fatty acids or soaps (5-50 wt %) as detergency builders and are formulated as stable oil-in-water microemulsions. The preferred surfactant systems comprise sulphonate or sulphate type anionic surfactants with minor amounts of ethoxylated nonionic surfactants such as C.sub.14-15 alcohol ethoxylates (7EO). Detergency builders may be present in amounts of 0.5-15 wt %, citrates being preferred.
EP 164 467A (Procter & Gamble) discloses laundry detergents and hard surface cleaners comprising oil-in-water microemulsions, containing alkylbenzene and olefin solvents, plus surfactants and substantial amounts of fatty acid soap. The compositions may contain ethoxylated nonionic surfactants, for example, C.sub.14-15 alcohol ethoxylate (7EO). Compositions containing sodium citrate as builder are disclosed.
In "Evaluation of Textile Detergent Efficiency of Microemulsions in Systems of Water, Nonionic Surfactant and Hydrocarbon at Low Temperature", J Dispersion Science and Technology, 6(5), 523-537 (1985), Marcel Dekker Inc, C Solans, J Garcia Dominguez and S E Friberg describe the use of such microemulsions for washing under conditions of minimum mechanical energy and at low temperatures. The systems studied contain C.sub.12 alkyl ethoxylate (4EO) nonionic surfactant, water and hexadecane, and optionally small amounts of cosurfactant (sodium dodecyl sulphate), or electrolyte (sodium tripolyphosphate or sodium citrate).
GB 2 194 547A (Colgate-Palmolive) discloses a clear single-phase liquid pre-spotting composition in the form of a microemulsion (oil-in-water or water-in-oil), solution or gel, comprising 10-70 wt % alkane (solvent), 4-60 wt % nonionic surfactant, optional cosurfactants and/or cosolvents, and 1-80 wt % water. It is suggested that builders such as sodium sesquicarbonate might be included, preferably at levels of 5 wt % and above. Unbuilt water-in-oil microemulsions are specifically disclosed which contain mixtures of the short-chain nonionic surfactant Neodol 91-6 in conjunction with the a longer-chain (C.sub.14-15) ethoxylated nonionic surfactant.